Insight into solvent effects on growth morphology of MgCO3.3H2O in CO2 mineralization: Molecular dynamics simulations and DFT studies

Experimental evidence shows that the solvent effect greatly affects the MgCO3.3H2O morphology, but the atomic-level mechanism still remains elusive. In this study, the influence mechanisms of H2O and EtOH on MgCO3.3H2O morphology were systematically investigated by a combination of crystal growth experiments, molecular dynamics (MD) simulations, and DFT calculations. In contrast to the traditional DFT calculations, the interface microenvironments were introduced to the crystal growth model first. The modified attachment energy (MAE) model proved that (1 0 1), (-1 0 1), and (0 1 1) surfaces dominate MgCO3.3H2O morphology in vacuum, H2O, and EtOH/H2O environments. The solvent molecules created an extensive H-bond network at solid-liquid interfaces, which greatly changed diffusion and combination during the crystal growth process. Compared to the H2O molecule, EtOH only forms H-bonds through the hydroxyl group. The CH3- end created some hydrophobic cavities, which led to weaker H-bond connectivity. The weaker H-bond network facilitated the removal of water from the crystal surface and strengthened the connection between the growth unit and surface, while reducing the solvent effect on the growth unit, thereby accelerating crystal growth and changing morphology. This study reveals the significant role of solvent in the crystallization process of MgCO3.3H2O, providing valuable insights for controlling the MgCO3.3H2O morphology at the atomic level.